The invention relates to a mechanism for forming an opening in a plastic part within a mold tool before removal of the plastic part from the mold tool.
Typically, holes or openings are made in plastic parts by a core pin inserted into a cavity of the mold during the molding operation. Plastic injected into the mold will flow around the core pin forming the opening. After the plastic has solidified, the core pin is retracted from the inner cavity of the mold to allow the completed part to be removed from the mold tool.
This method of forming holes or openings is problematic for certain plastic materials and molding conditions. Plastic flowing around the core pin forms a knit line. The knit line is a term of art referring to a seam or inconsistency in the plastic part caused by two fronts of plastic failing to completely mix before the plastic solidifies. The molten plastic material flowing around the core pin forms two fronts. These fronts of plastic flow may begin to solidify before merging with each other on the opposite side of the core pin. This phenomenon creates knit lines that cause poor aesthetic appearance and weak points in the completed plastic part.
Another typical method of forming openings in plastic molded parts is byway of secondary boring or drilling operations. This is accomplished by removing the part from the mold and transporting the part to another workstation where the openings are machined into the plastic part. As appreciated, machining the opening or holes is an expensive and time-consuming process that increases the cost of the finished product.
Accordingly, it is desirable to develop an apparatus and method for forming opening within molded parts without additional machining process while minimizing formation of weak points within a molded part.